Process of dyeing with vat dyes



Patented May 4, 1943 2,318,133 I I i PROCESS or? DYEING wrrn va'rnvns 7William M. Wentz, Carneys Point, N. J;, assignor to E. I. du Pont deNemours & Company, Wilmington, Del., a corporation of Delaware NoDrawing. Application Deccmber'31, 1940, Serial N0. 372,578

11 Claims. (01. 8-34) This invention relates to a process of dyeing withvat dyes and more particularly to an improved process for applying vatdyes to fabrics duced in such solution with reducingagents, such as withsodium -hydrosulfla, to the leuco known method of vat dyeing where evenmediumly strong shades were required; I

Modified derivatives of the vat fcolors have been produced with the hopeof finding a method of applying the vat colors to the alkali sensitivefibers by methods that would not require strong alkalies. Asillustrative of f this type arethe dyes known in the trade as Indigosolswhich are leuco sulphuric acid esters of certain vat colors which aredyed from an aqueous solution and developed by means of diluteacids andsuitable oxidizing agents which are not as harmful to wool, silk andcellulose acetate as are the strong alkalies. These colors, however, arevery.

form, which as the alkali metal salt is-quit 15 expensive t manufactureand e difficult t v "'yappirto-fibers in even mediumly strong shadessoluble in relatively strong alkali solutions but is much less solublein solutions of low alkalinity. The process of dissolving vat colors inalkaline hydrosulfite solutions is usually referred to as vatting.

While certain of the vat colors when in the form of the alkali'metalsalts of the leuco are soluble in sodium carbonate solutions insulficient amount to permit dyeing fibers'from such a solution in weakshades, the class as a whole and particularly those of the anthraquinoneseries are not sufficiently soluble in such alkaline solution to permit,the preparation of comv mercially satisfactory dyeings therefrom.

Because it is necessary to use the vat dyes in a caustic alkalisolutions their use has been limited almost exclusively to the dyeing ofcotton or other cellulose fibers, for silk, wooland cellulose acetateare deleteriously affected by caustic alkali solutions of the strengthnormally used in vat dyeing.

With the development of the newer fibers such as cellulose rayons,cellulose acetate, nylon, etc., great advances have been made in fabricdesign by mixing these fibers with wool, silk and cotton. For instance,viscose rayon in filament or staple form, cellulose acetate, wool, silkor nylon may be woven as effect threads with cotton or with each otheror they may be mixed in staple form to give threads from which manynovel and vale uable fabrics may be produced, and many such fabrics areon the market today.

The advance of these new fabrics, however, has been retarded somewhatbecause of the difiiculties encountered in dyeing them in fast shadesfor the fast colors of the vat dye class could not be commerciallyapplied to the alkali sensitive fibers or to goods containing suchfibers by the usual methods of dyeing, or by any previously because oftheirflirhithd solubilityin. "water and their lack of substantivity formostfibers,

known as the continuous piece goods dyeing.

process wherein the fabric ispassedthrough the padder, developing bath,oxidizing bath} soaper, etc., in a continuous piece.- Such con-s tinuousdyeing processes introduce difiiculties that arenot experienced in theordinary "batch dyeingprocesses, although in certain cases thecontinuous process permits the application of vat dyestuffs to fabricsthat could not ordinarily be dyed with vat dyes by the batch process.Because of the speed with which the fiber passes through the causticalkali solution certain fabrics containing caustic alkali sensitivefibers such as wool and cellulose acetate could be dyed with outharmfully affecting such sensitive fibers; where the temperature andtime of treatment. were held at a minimum. Such process, however, can beused only for dyeing in verylight shades, because the restrictedconditions do not permit sufficient absorption of the dyeto give bypassing the material, after being padded with norrna lIy takes p1aceinthe alkalinity of the re-reduction bath. Q Hebden, U. S. 1,148,966,describes a process for dyeing with rat colors by the batch process inwhich the color is forced on the goods by progressively diminishing thesolvent capacity of the bath fontheileuco compound during the dyeingoperation. .It-is also alleged that this method can beemployed in thedyeing of animal fibers with vat dyes, although the process has neverbeen commercially successful for such fibers. This process, however, cannot be applied to con-- tinuous. piece goods dyeing processes. a

In the continuous piece goods dyeing of cotton fabrics by a process suchas described, for instance, in the-Tlce patent above mentioned, the

re-reduction bath isoriginally charged with the same color that is usedin the padding bath, caustic soda and sodium hydrosulflte but in reducedconcentrations. However, the chemical reaction which normally occurs,due to the reduction of theyatdye and to exposure of the hydrosulflte onthe goods and in the open vat 'as'it comes in contact with air, formssodium bisulflte and sodium bisulfate which react with the caustic sodain the re-reduction bath to form sodium sulfite and sulfate. These saltsexert a salting'out action in the dye bath, tending to change thestrength of dyeing as the goods passes there-through as the ccncentratiOHSISmOIB m: y escribed by Hebden. Because the caustic soda in there-reducing bath is used up due to the oxidation of the-hydrosulfite itwas found that the re-reduction bath finally became acid causinprecipitation of the dye from the solution unless additional caustic isadded. In the continuous piece goods dyeing of cotton by the Ticeprocess, theloose improperly fixed color,

' together with some of the color that is actually fixed but which canbe stripped off with alkaline sodium hydrosulilte' is capable of beingdissolved in the re-reduction bath and bleeds off until an otherchemicals necessary forthe dyeing operation.

It is a further object of the invention to provide a commercial methodfor dyeing animal fibers or mixed goods containing animal fibers and/orhydrolyzable cellulose esters or ethers with vat dyestuffs withoutharmful effect to such alkali sensitive fibers.

I have found that in continuous processes for dyeing piece goods withvat colors uniform dyeings can be obtained with a minimum consumption ofcolor and other chemicals by padding the goods with the usual causticalkaline solution of the reduced color and then subjecting the goodswhile the color is still in a substantially reduced state to adevelopment with an alkaline hydrosulfite or similar reducing agentsolution in which the alkalinity is maintained sufficiently high toretain the color in solution at all times,

but which hasapH value materially less than that of a caustic alkalinehydrosulfite solution,

and which can be maintained at predetermined ing the piece goods whichhave been padded with the usual caustic alkaline hydrosulfite solutionof a vat dye or dyes into a developing bath comprising an alkali metalcarbonate, an alkali metal equilibrium is reached where the amount ofSince the aifinity of these vat colors for fabrics varies with thealkalinity of the dye bath any change in the alkalinity in there-reduction bath shifts the equilibrium to cause a greater or lessamount of dye to be absorbed by the fiber or to go into solution in thedye bath. As long as there are fluctuations in the alkalinity of there-reduction bath material variations in the resulting dyeings arenoted. It was therefore found necessaryto continually add caustic sodato the re-reduction bath to maintain as near as possible uniformconditions but 'due to the chemical reactions as above pointed out itwas found to be necessary to add considerable quantitles of caustic sodato maintain the original dyeing conditions and that due to the rapidaccumulation of the salts in the bath some means had to be devised forpreventing their accumulation. 'I'his'was done by the addition of waterwith continuous draining oil of part of the solution. Any water drainedoil also carries some valuable dye which must be continually replacedeither by addition or by bleeding from the goods being dyed. Thisprocess, because of theuse of hydrosulfite and a small amount of thecolor employed in the original vat. the color is fixed in the fiber anduniform shades are obtained as long as the development solution ismaintained with sodium carbonate to give sodium bicarbonate and'sodiumsulfate. The accumulation of the undesirable salts in the solution istherefore at a very much reduced rate as compared with the process inwhich caustic soda is employed as the alkali in the developing bath. Thesodium bicarbonate formed in the reaction reacts with the sodiumhydroxide being brought in on the fiber from the original pad liquor toform more sodium carbonate inthe developing bath.

This obviates the addiudn or further alkali as long as undue oxidationof the hydrosulfite is not experienced such as when there is too long acontact with air or Whenworking with pile fabrics or other very looselywoven fabrics which carry larger quantities of adsorbed air into thedevelopment bath, or when the run is of such a length that the sodiumcarbonate reserve falls below the ascertained limits for any particularset of conditions. When dyeing such goods larger amounts of caustic areusually employed in the adding liquor, although if desired, additional x33 the, eq'uilibriun l between the amount of coin caustic bdevelopliientjpath bonate are forined due to the 'abs'oi ption of one: 1

terial quantities .of carbonqdioxldei fom the air 5 by the caustic sodasolution in: the padding liquor both on the goods and in. the vat. Thissodium carbonate is detrimental'wh'ere'.Caustic soda alka- -i nity isdesired but is ,a necessary and desired 311; tojperrnit the us ofthesewaker alliali'es in the developingba't h Whileoiiie fthe colorsparticularlfir of th indi'goic l olasa in the "luc'o' f or n are readilysoluble s luupn s navlng s 151-1 0; as low as}; 8, others}partioularlymosebr jthe' 'anthraquinone floss usually requiregin-alkali'n hydrosulfite solution oiia pHotmpr-aboiiej Tneem'lre rangeo'f'- vat C0 are when aoblled tothe cloth from the or'dinary causticalkaline sodium carbonate alkallnexhydrosulfite solution (provided noundue oxidation has oqourred) to permitcomplete developuient" t olorfor: the fiber when it is treated in such a solution; In

51 1 1 01 theig'olor orithe f-a-brio as the padded'material- Ieai es'th'e padding "solutiom sodium 1 oanbonate hydrosulfite is f sumcientlystrong to rereduce the? "oxidized" color; and 'oa'use fixation.

However: Withi a few I of the anthraquinone vat e ga ore, suol'l' asthe. 110'rilia'ted' indanthrone, earejs'h be'take" tobre'i'ent undueoxidation he fiber in t e inte'rva1"oftiine 'betweenthe jpa anddevelopment' operation because ot 1 the jdii fiioultfekpriehoedinbrereducing :such

b016 5; With iiat' colols, nii'ld alkalies having; a pH? l wer {mgn-*-10may be employed; :iThe limits of alkalinity-Witliin Which"a particulari"color is sumciently soluble can be readily-determined 70 by a simpleexperimentationl' As long as the color is slightly soluble in Ithedeyelopment baththe alkalinityfjof that solution mayfbe maintained atany predetermined"pointgabovethat at which-the color is 'precipltateujwhile ig-above stated, s

lower-l alkalinity employed :;in:-:;the:; deyelopn entquickly'es'tabllshem becauseof: the small amq t;

in'tsolution' when noaustic, soda sis usedtzgthlisi 50 hydrosulfite vatare sufiiciently soluble in athe mel g'o *orthebeudeo'materiarandithat-goinfg; on 'ffoni' the-development liath changeswith l in the alkaliiilty} when onceithe-sequiez abllshed-and' that 1set of? oonditions;

' the depth or shade of 'thel res ultw f rrespeotlve of whether tstin'this sollitibfiis advisable; partidularly until bi 'oper running"condition's 'arei'establishedz 'hieh neriodio fcheck's are madetordetectI any trend awayiron'l' *the starting .jcondi'tionsz; vWheresodium carbonate is employedtauxiliary; teklsotfeaustio l soda;- sodiumcarbonateiand; sol diunifi bloarbon'ate arei made r-liesitdiltr;:availablaln;v case unfIoi-eseen:conditions:'zarise-rwhicmcauae-za; variation inthefalkalinityrbeyond:theji'toleranoes allowable Whermropei-arunning;conditions are; established origlnallylawithi manyifahrios: only; minorarid sometimesnq'additionsneedgbe; made;

to the development bath fonrrunsot'lseveral thou:

bathythe equllibrium wlth regardit the color is of color in solution;as'compared'wlthgthegaino ing a materl'al savlnggpartlcularly in .;shortcloth: where -:the 300.10! or: c019 emp oyed, 3 i?" sin el msp l s n ded t o ta daa t ee il rmm thi me n min ster al 19 lbiin he u ua mim halkali metal hydrosulfite or othe h l and re erab y wi th' dmo'n 9rsuitablepenetrating and -fo M mrbl resent such as now employed in ;;thert, The alkali o a o ss thqvnddin q1iri11 dev j upon the nature of theparticular we ooloriin} volved ,in the depthot shade and a the type- '61a ab icbeing y yed-wf 'srfia u ht it'yl nd :an-excess of them uclngagentare always main.- a e -w ...After.-..-the dyed- 489 1151 a ted s v.veloping bath it is oxidized rinfsed, 'soa'p'ed, rinsed, d ied andyfinishe eh s memo f 1 9. nl yed'for thet veular we. otl t 'VQ1Ved,* Bythe :oontinuous 'dyeing' p "refermore particularly; ho fbro cess A N thysoods is a sed; 7 e t v r0 3 'hebad summ n athroughthe degelopment,thMWeIalso .those continuous. piece T Wifli Elli- M nm -n e i t m v ablerange of anmumty' whioh firaotioe has shown will not cause any shadevariationa T0 bef sure;

J that the alkali'nity of tlie 'developmrit 1 m 's maintai 'ed co"tarit; "continualsainolingeand llpeluqe wherein the goods istransferred from one machine to another between thepadding anddevelopingoperations. goods must be batched off the padder and cannot bereadily transferred to another machine, such I transfer operation.

I have found that satisfactory results can be obtained if the goods tobe batched 0113 is passed throughv a solution containingv approximately1% of sodium carbonate between the padding and batching operation. It isof course understood that in the padding, developing and in thebatching-off steps the goodsis passed through the squeeze or nip rollsusually employedin the dyeing processes whereby the' amount of liquidremaining in the fabric can be controlled.

In the dyeing of cellulose rayons and other fabrics containing alkalisensitivefibers it is often impossible, due to their low tensilestrength when wet, to dye 'this type of-goods in the usual continuouspiece goods dyeing equipment because of the tension required on thegoods.

This tension also stretches the goods and imparts In such cases wherethe 7 controlpurposes by titration with certain indicators. Thefollowing practical methods have been developed fordetermining thealkalinity .in terms of sodium bicarbonate or caustic soda content, andfor determining the total alkalinity,

of the developing carbonate. V

0 cc. of the solution from the development solution interms of sodiumbath are placed in a small beaker or Erlenmeyer flask and 15 cc. of 10%barium chloride solutionare added- After the addition of phenolphthaleinthe solution .is titrated with N/10 NaQH if the solution is acid or with10/N H01 if the solution is alkaline. While the end-point is somewhatobscure it may be readily estimated within 0.5 cc. of the N/10solutions. The first end-point should be taken for with the presenceundesirable effects which cannot be' corrected in V subsequentoperations. By using sodium car-.

bonate or otherweak alkali inthe development bath such'gohdscan be dyedby padding in the in cases where the dye employed is extremely sen--sitive to air oxidation. It is therefore to be understood that the useof mild alkalies in the developing bath according to this invention isnot limited to continuous dyeing processes.

Where sodium carbonate is employed the amount may vary within widelimits for its alkalinity is such that alkali sensitive fibers are notdetrimentally affected by it. A sufficient quantity should be used tomaintain the color in the developing bath in solution and a reserve toprevent the solution from becoming too low in alkalinity before theproper adjustments can be made. From 0.5 to 2.5 ounces per gallon willusually be found to be suflicient for-proper operation;

The amount of alkali metal hydrosulfite in the developing bath should besufficient to keep the color in the reduced state. A substantial excessof hydrosulfite is desirable. Limits of from 0.15 to 0.5 ounce pergallon are adequate for proper operation and control.

While in determining what mild alkalies may be employed in thedeveloping bath and the concentrations in which they may be used the pHvalues maybe determined by the usual colormetric or electrometricmethods inwater solutions, it has been found that the alkalinity of whodeveloping bath which contains oxidizing and reducing agents can best bedetermined for of the other'salts in the solution the end-point willshift as the solution stands. The entire determination'should thereforebe carried out as quickly as possible The amount of sodium bicarbonateor. sodium hydroxide may then be determined by the following formulapercent NaliC 03 cc. HClXNX LO 50 -pcrcent NaOli Having determined theamount of either caustic or bicarbonate present in the developing bathbyrthe barium chloride titration method as above described the totalalkalinity of the bath may be titrated directly with HCl usingphenolphthalein as theindicator. By taking into consideration the bariumchloride finding the differ ence inithe titrations may be considered asso-v dium carbonate. c r

The necessary sodium hydrosulfite concentration should, of course, bemaintained in the development bath. Tne amount of sodium hydrosulfitecan readily be determined by titrating a known amount of a standardsolutionof sulfonated indigo as follows:

Pipette 5 cc. of standard indigo solution into 'a 250 cc. Erlenmeyerflask, dilute with '75 cc. of water. Titrate as rapidly as possible withthe Na2S2O4 solution taken directly from the development bath with a 25cc. calibrated pipette until 1 drop causes the blue color of the indigoto disappear.

, ,(Zalculation fl ew cc. Nazszol (developing solution) -purcent Nazszoiby volume The sulfonated indigo solution may be prepared as follows:Weigh 3.76 grams of finely allow the solution, to stand for at leastone-half hour before using.

EXAMPLE 1 Jean cloth running 2.85 yards to the pound in the form ofpiece goods is dyed in desirabletan shades suitable for cotton workclothing by the continuous process as follows:

The cloth is impregnated or padded in the open width by passing itthrough a padding bath held at 120 F. and containing 20 gallons of thevatted color made up as follows:

A penetrating and foam control agent such as the fatty alcohol sulfateModinal D 0.1

at the rate of about 70 yards per minute. The

goods is then passed through squeeze rolls mounted over the pan or padbox adjusted so that the material carries approximately 60% of its dryweight of the padding solution. The pad liquor taken outby the cloth isconstantly replaced by additional pad liquor known as the pad Afterpadding, the cloth is passed at the same speed, with the color still insubstantially reduced state, through a development bath where it istreated for three minutes. This development bath consists of two 1700gallon boxes fitted with rollers to lead the cloth up and down throughthe boxes in a progressive manner in such a manner that approximately210 yards of cloth are immersed in the 3400 gallons of solution atanyone time. veloping solution comprising 3400 gallons of water containing1.5 oz. per gallon of sodium carbonate and 0.25 oz. per gallon of sodiumhydrosulfite. The temperature is brought to 150 F. and a color solutionmade up as follows is added:

- Pounds "Ponsol Brown AG double paste 4.68 Ponsol Olive AR-.. 0.05Ponsol Brown VR. 0.18

are reduced in 20 gallons of water with 2 pounds of sodium hydroxide,and 1% pounds of sodium hydrosulfite. Two-thirds of this color mixtureare added to the first 1700 gallons of solution in the first bath andone-thirdis added to the 1700 gallons of solution in the second bath.Seven hundred pounds of salt (NaCl) are added to each 1700 gallons ofwater. This amount of color closely approximates equilibrium at thestart. The solution is then titrated=to determine if These boxes arecharged with a de-' I talned. Experience has shown that a tolerance of1.4 to 1.6 oz. per gallon of sodium carbonate in the development bath ispermissible forthis type of cloth. The amount of hydrosulfite present inthe development bath should also be checked from time to time and thestarting concentra tion of .25 oz. per gallon of sodium hydrosulfiteshould be maintained. Experience shows that a drop to .18 oz. per gallonof hydrosulfite is permissible on this type of cloth; Approximately 15pounds ofsodium hydrosulfite must be ,added to the development'per hourtov maintain proper concentration, where the goods is being passedthroughthe solutions at the speed mentioned.

Under the above conditions the alkalinity of the development bath stayswithin the degree of tolerance mentioned without auxiliary feeds ofsodium bicarbonate or sodium hydroxide.- However, auxiliary feedsofthese materials and an auxiliary feed of sodium carbonate should bemade conveniently available foruse should the control tests indicate atrend requiring theiruse. After development, the goods is washed withwater, oxidized with a solution of sodium dichromate and acetic acid,rinsed, soaped, rinsed, dried and finished in the usual manner.

By this method, a saving of 11.2 pounds of color in the development bathis made for a 20,000 yard run as compared with the amount of colornecessary where caustic soda is employed with the same amount of salt inthe developing solution,

, or a saving of 70% in color used in the developing'. A furthermaterial saving in alkali and other chemicals employed was experienceddue to the use of sodiumcarbonate in place of caustic soda, foradditional feed of alkali is not required, and because with the loweralkalinity, less 7 color required in the solution for maintaining 1 thiscolor equilibrium, and because the alkalinity of the solution is readilycontrolled, much more uniform dyeings are obtained than where causticsoda is employed.

While in the mild alkaline developing bath the addition of inert saltssuch as sodium chloride and sodium sulfate further reduces the amount,of color required to establish equilibrium in-the same manner as whencaustic alkali is used, with any sodium bicarbonate is present in thesolution by the barium chloride method above described and anybicarbonate present is converted to sodium carbonate with the necessaryamountof caustic soda. This usually requires from .05 to .1 oz. pergallon of caustic soda. After the continuous dyeing has started periodictests are many colors and certain fabrics the use of large amounts ofsalt is not advisable. With the weak alkalies however, salt is notnecessary for the solubility of the colors is small as compared withtheir solubility in caustic alkali. Where caustic alkali is .usedwithout salt almost prohibitive amounts of color are required in thedeveloping bath, particularly where the more soluble colors are used andmore particularly where small yardages of goods are being dyed, for thedye remaining in the developing bath cannot be recovered. Furthermore,color equilibrium is exceedingly difficult to reach in the causticalkali developing bath whensalt is not employed. A

While a single developing bathmay be employed, a series of'two or moreis ordinarily used with diminishing amounts of color in each bath.

This materially reduces the amount of color required in the developmentfor as more and more i of .the color is fixed on the fiber, less coloris required in the developing bath to establish the color equilibrium.Where only a single bath is the developing bath under the conditionsorig-1 colors by the continuous dyeing process as dcs'cribed inExample 1. The padder which is equipped'with' a 30 gallon pad box ischarged with 30*gallons of the vatted color made up as above describedwith:

= Ounces per gallon Ponsol Brown VR paste; 0.567 Ponsol Olive GGL paste0.413 Ponsol Brown AR dbl. paste 0.495 Caustic soda (dry) 1.750 Sodiumhydrosulflte 1.500 ModinaP' D 0.10

and is held at a temperature of 120 F. The pad feed is made up asdescribedin Example 1 with:

Ounces per gallon Ponsol" Brown VR paste 0.63 Ponsol Olive GGL paste0.59 PonsoP' Brown AR dbl. paste 0.55 Caustic soda (dry) 1.75 Sodiumhydrosulfite 1.50 Modlnal D 0.10

Alter paddingthe cloth, it is passed while the color is stillsubstantially in reduced form into a developing bath where it is treatedfor three -minutes at 145 F. In this case, a developing bath consists of4 six hundred gallon boxes fitted with rollers to lead the cloth fromthe top to the bottom of the boxes in such a fashion that 90 yards ofcloth are immersed in the 2400 gallons. The boxes are charged with thetotal of 2400 gallons of water containing sodium carbonate equivalent to1.25 oz. per gallon and sodium hydrosulfite equivalent to 0.25 oz. pergallon.

"I W f f Ounces Ponsol .Brown VR paste ,7.40 "Ponsol" Olive GGL paste3.00 Ponsol Brown AR. dbl. paste 6.50

are reduced and dissolved in. 11 gallons of water with Zpounds causticsoda (dry) "and 2 pounds sodiumhydrosulfite at 120? F. Six gallons ofthis color solution is added to the first box.- Three gallons to thesecond and one gallon each to the third and fourth boxes. The developingsolution is then titrated for sodium bicarbonate and adjusted as inExample 1. The dyeing is run at 30 yards per minute. By periodicaldeterminations the alkalinity of the developing solution is maintainedas closely as possible to the starting conditions. Tolerances of from1.20 to 1.35 oz. per gallon of sodium carbonate, .01 oz. per gallon ofcaustic soda and .05 oz. per gallon of soduim bicarbonate arepermissible.

Under these conditions and with this type of cloth it is not desirable'to control the alkalinity in the developing bath by increasingtheamount of causticsoda in the pad feed because of the deleterious effect'it may have on the alkaline sensitive fibers in the fabric and since indyeing: fabrics containing animal fibers by this method there ,is'fafaster neutralization of thealkali in the development bath, auxiliaryfeeds of caustic soda are usually necessary; After development, thegoods is given a running rinse'with water,

skyed to the air to oxidize the color, and then soaped,-rinsed, dried,and'finished. The goods thus dyed is fast to laundering and dry cleaningand tests indicate that there is substantially no deterioration of thealkali sensitive fibers.

EXAMPLE 3 Suiting material comprising spun viscose rayon with an acetatestripeand blend in which the.

I Ounces per gallon Ponsol Blue 3G paste 4.73 Ponsol Violet BNX Supra0.425 Caustic soda (dry) 1.75 Sodium hydrosulfite 1.50

The auxiliary pad feed of this color comprises:

Ounces per gallon PonsoP Blue 3G paste 5.5 Ponso1" Violet BNX Supra 0.5Caustic soda (dry) -1 1.75 Sodium hydrosulflte 1.50

which is made up and held at 130 F. The padded goods may bedeveloped ineither of two ways:

A. By the continuous process in which the goods passes directly from thepadder while the color is still in the substantially reduced state intoa developing bath consisting of three eight hundred gallon boxes fittedwith rollers which lead the cloth from the top to the bottom of theboxes in a progressive manner and in such a fashion that approximately120 yards of cloth are immersed in a total of 2400 gallons at a time.The developing boxes are charged with 2400 gallons of water containing1.25ozs. per gallon of sodium carbonate and 0.25 oz. per gallon sodiumhydrosulfite. Seven gallons of color for use in the developing bath wasprepared by dissolving in 7 gallons of water:

Ounces per gallon Ponsol Blue 3G paste 22 Ponsol" Violet BNX Supra 2Caustic soda (dry) 6 Sodium hydrosulfite 6 at a temperature of 130 F.Four gallons of this mixture were added to the first box after thepadder, two gallons to the second box and one gallon to the third box.The temperature of the development bath is brought to F. after the usualcorrection for any sodium bicarbonate present. The run of the goodsthrough the developingbath is started and the sodium carbonatealkalinity is maintained within the tolerance of from 1.20 to 1.35 ozs.per gallon. The caustic soda should not go above .02 oz. per gallon andthe bicarbonate should not go above .05 oz. per gallon while the sodiumhydrosulfite should be maintained at not less than .18 oz. per gallon.Under the above conditions with this type of cloth it is not desirableto control the alkalinity in the developing bath by increasing theamount of caustic to pad feed and therefore auxiliary feeds of causticsoda, sodium carbonate and sodium bicarbonate are mad convenientlyavailable should the control tests made during the continuous runindieate a trend beyond the tolerance above indica ed.

The goods as it passes from the development bathis rinsed with water,oxidized with sodium perborate, rinsed, soaped, rinsed, driedandfinishedinthe usual manner. I

- B. The development may also be carried out on the reel or dye becktype of apparatus inwhich case the goods as it passes from the padder'isgiven a wash in a 1% solution of sodium carbonate. Four hundred andeighty'yards of goods at a time are then transferred and loaded on tothe in the rope form. The dye beck is previously charged with 1050gallons'of water containing 1.25 ozs. of sodium carbonate per gallon.The

temperature is brought to 150 F. and the goods is turned in thissolution for five minutes. While reel dye machine or dye beckWhereitis-handled the goods is in motion sodium hydrosulfite equivalentto 0.25 oz. per gallon and caustic soda equivalent to .05 oz. per gallonare added. The goods is moved in the solution for 15 minutes afterwhichit is given a running wash with clear wa ter, oxidized withhydrogen peroxide, rinsed, soaped at 150 F., rinsed, dried and finishedin the usual manner. Since the development in this case is carried outas a unit with continued repassage of the goods through the same bathand the hydrosulfite is added after the goods are in motion in thesolution color need not be added to this developing bath.

EXAMPLE 4 EXAMPLE 5 Upholstery pile fabric having a cotton back'andmohair face may be dyed with vat colors by the process asabovedescribed. The vat colors are selected to produce certain styling orcolor A as above described, was ubjecte balance between the cotton backand mohair face v i and also to produce superlative fastnessparticularly to light. The following exam-ples are given whichillustrate the dyeing of these mixed fiber fabrics and the possibilityof color selections for,

such materials. In these examples the fabric is padded with the causticalkaline solution of the vat color and while the color is still insubstantially reduced state it is subjected to development in a bathcontaining 1.25 ozs. per gallon of sodium carbonate and..25 oz, pergallon of sodium hydrosulfi'te and the ascertained amount of-color toefiect equilibrium for a period of three minutes at 145 F. In all casesthe padding liquors are prepared'by dispersing the vat colors inwater,adding'1.75 ozs. per gallon of caustic soda (dry), bringing to theproper vatting temperature and adding 1.5 ozs. per gallon of sodiumhydrosulfite.

The concentration of color and the vattingtemperatures are given withthe description of the dyeing effects produced.

A. Eight ozs. per gallon Ponsol Red BN double paste, padded at 120F.,'dyes both the cotton back and mohair pile in red shades brighter inshade than the mohair pile. it I exhibits good light fastness.

F. The mixtureoi 0.5..oziper gallon SuIfanthrene 0 green shade with vatcolors giving desirable'con is'made up of:

.After padding, the cloth is batched on ashelli I given two passagesthrough the sodium carbonate sage through the solution. This.development C. Eight ozs. :per gallonf Ponsol Yellow AR, V, padded atfR. dyes, cotton to aboutthe same ;depth-but i'gieener and: brighter thanthe mohair pile; I It; exhibits. excellent rest,-

ness to lightl w, I D. Two ozs.-per gallon Ponsolifyellowf'Gdouble;. g Ipaste, padded";"atrg lliil Il.-, -=dyes'thefcotto'n very' muchheavierthanthen ohairl' r E. Three ozs. per gallon sulfanthrene .Brown Gpaste, padded=atl40i-Fgj-dyes the cotton verymuchlightershade"thansthemohair.

7 ew standard abrasion test andnodete'r'iorat'ion of the moha r.w s is ri le -v L'Exmrtaca A mixed fiberfor men sxsuit'simade ofcotton, 4viscose staple rayon and. woolis dyed in astone trasting color effectsbypaddln'g the'clothwitn 5 the vat dye padding'solution in' a {manner' dscribed in Example 1 in whichthe padding li'qu v i Ounces per gallonPonsol Direct Black 33 dbl. paste." Ponsol Green 2BL 0.4 Caustic soda(dry)' "l"."75 Sodium hydrosulfite 1.75

The padding is carried out at a temperature of F. The pad feed was madeup as follows:

i 'Ouncespergalloi'i v Ponsol Direct Black 3G dbLpaste 3.0 Ponsol Green2B1; 0.5,, Caustic soda iig 1,75 Sodium hydrosu1'flte 1175v andimmediatelytransferredto a jig..; The ,jig;

is previously charged with 80-gallons of a solution containing 1 ozs. ofsodium carbonate main tained ata temperature of F. The cloth is solutionby running the; cloth down from the j shell on to the jig] beam and thenpassing back on to the second jig beam. v; 0.25 oz.- per gallon, ofsodium hydrosulfite is then added to the carbonate solution and aftertitratingfor sodium bicarbonate, alkalinityand total alkalinity it isadjustedso as to contai'nl ,1, ozs. per gallonsodium carbonate and 0.05oz per gallon of caustic soda.. "Whilethe solution is maintained at 150the cloth is given apasbath is again titrated and adjusted. The ge Ivelopment requires from 2 to 4 passages, depend: j

..-Sod

passed directly from'thepadder'into a continuous ing onthe depth orshade, size "of. roll and the ,nun'iber of "yards on the roll, The bathshould I be testedfor alkalinity between the passes and indicatedadjustments madei. After development the cloth is given twopassages incold water, two

passages through'an. oxidizing bath then rinsed, soaped yrinsed'andidried in the usual manner. I Y T A mixed fiber fabric containing80% spun ,vis-

cose rayon and 2.0% w'ool..i s..dyed.a solid bright blue shade with vatcolorsiby the process of Exampledjb y employing for, the paddingsolution 'V fQuncesper'gallon fBlu MR 4.0

Bons'ol Green 2'13 0.5 caustic sodadry'u's, 1.5 hydrosulfitearm 1.5

yeing'is carriedoutat 140% F. The cloth is reel dyeing'machine"containing; thev development bath of sodium carbonatefsodium.hydrosulfite,

l. and' sufficient amount :of -thercolors to "approxiinmate?!equilibrium v,withw the padded material. Limits of.0'2'oz. per gallon;of caustic soda and. .05

oz. per gallon -of:ssodium(bicarbonate should be maintainedfiiThesodium" carbonate concentrae, tlon'should beheld at l20 to "l.3 5 ozs.per gallon,

I v andthe sodium hydr'osulfiteshould not fall-below'.18oz'. per-gallon.The reel dyeing machine is so arrangedv thatthecloth ,is stillin theopen that have been dyed on cotton, and; on'mixed" fiber fabrics.containing spun rayon and wool without showing any harmful .efiect onthe alkali sensitive fibers where the goods were padded at" 130 F. witha vat solution made up as follows:

. Ounces per gallon Ponsol Direct. Black 36 double paste 4.0

I Caustic soda (-dry) 1.80

width-when it .enters the machine, After immersion in the open widththefcloth goes into the rope form in which form ,itremains for thedevelopment, oxidationand soaping operations.

librarians-8 I A viscose staple spunrayon fabric is dyed in blue shadesfast to light and washing by nip padding with a solution of thevattedcolor prepared from I Ounces per gallon ."Po'nsolu Blue BF double pastee 2.0

I Ponsol Violet BN supra .25 Ponsol". Olive GGL paste .25 Potassiumhydroxide 1.75

Sodium hydrosulfite 1.5

The goods is passed from the padder through a developing bath, asdescribed in Example 1, in

which the required amount" of colors have been added to approximatecolor equilibrium at the start... The alkalinity of the developing bathis maintained from 1.4 to 1.6 ozs. per gallon of sodiurn'carbonateandfrom 0.02 to 0.05 oz. per gallon of sodium hydroxide. Due to the natureof this combination of colors, bicarbonate alkalinity in the bath is tobe avoided. The hydrosulfite should not be allowed to fall below .18 oz.per gallon." I

Other alkaline salts than sodium carbonate may be employed for thedevelopment of these vat colors, provided they are sufficiently alkalineto maintain the reduced vat dye in solution, and, where'the processis-used on alkali sensitive fibers, the alkalinity is not of such a;strength that it injures such materials in the time requiredfor'developrnent. Alkaline solutions of between pHof 8 and pH 12 havebeen found to be satis-- factory.

The following salts and combination of salts,

which in water solutions have a pH value in the concentrations used asindicated, have been found to be suitable for developing vat dyes of alltypes Sodium hydrosulfite 1.50

The padded goods were developed for 3 minutes at F..in a developing bathcontaining 0.25 oz, per gallon of sodium 'hydrosulfite and the followingamount of alkaline salt or mixture of salts:

(a) 1.5 oz. per gallon sodium carbonate (pH 11.25) (bi 1.5'oz. pergallon sodium phosphate (NazPOa) H 11.93) ell/fixture of:

' 0.938 oz. per gallon NaaPO4 0.56 oz. per gallon Na2HPO4} (pH 11'44)(d) 2.5 ozs. per gallon potassium carbonate (pH (e) 1.5 ozs. per gallon42. B. NazSiOa (pH 10.49)

Satisfactory color shade development was obtained in all cases.

The pH measurements for the above solutions were made prior to theaddition of the hydrosulsodium hy- PH 11.8)

fite with a hydrogen electrode using a saturated calomelelectrode as areference electrode. The

hydrogen electrode was checked against a standard'buffer solution of pH10.00 before and after the measurements'were made. I

While in the above examples, standard commercial vat dyes of theanthraquinone and indigoid types are used, it is to be understood thatthe invention is not limited to these particular colors but isapplicable to all vat dyes, such as those of'the anthraquinone, indigo,thioindigo The invention is of particular importance in the dyeing ofthose and sulfur vat dye classes.

colors'that must be used in caustic alkali solutions for by the presentprocess these colors can be applied to fabrics containing wool; silk andcellulose acetate rayons;

As illustrated in the above specific examples it is usually necessary indip padding to have the pad feed somewhat stronger in dye content thanthe initial padding solution, for, due to the affinity of the color forthe cloth there is relatively more color than water retained by thecloth. This causes a partial exhaustion of the.

color in the pad box. -To correct this the pad liquor fedinto the padbox to replace that taken up by the cloth must contain a proper amountof additional color to maintain the starting concentrations; Unless thisis done a taper or progressive loss in depth of shade will result when asingle "color is used and a taper in both depth and shade will resultwhen a mixture of colors is used which have different rates of exhaust.

It has been" found that complete development of the color in the mildalkaline development bath requires about three minutes or more. The timeof development may be decreased but only with a possible sacrifice offastness and color economy.

It will be obvious that this process for developing vat dyes is notlimited to piece goods dyeing. This process makes possible the dyeing offibers, and particularly the alkali sensitivefibers with vat dyes in anyform such asv in skeins, warps, slivers, etc., provided the material canbe impregnated, squeezed and passed into the development bath beforedeterioration of the alkali sensitive fibers takes place.

It is to be understood that the amount of sodium carbonate in thedeveloping bath can vary within wide, limits provided the startingamounts are maintained within relatively narrow limits. From thestandpoint of control the starting sodium carbonate concentration.should be set high so that the total alkalinity of the devel oping bathis not subject to wide variations in short periods of time.

I claim:

1. In the process for dyeing textile fibers with vat colors the stepswhich comprise padding the fibers with a caustic alkali solution of there-' vat colors the steps which comprise padding the fibers with acaustic alkali solution of the reduced colors and developing the colorson the fibers by subjecting them, while the color is in substantiallythe reduced form, to a mild alkaline solution of an alkali metalhydrosulfite until development of the color is substantially complete,said developing solution having an alkalinity of from about pH 8 toabout pH 12 and maintaining the alkalinity of the solutionrelativelyconstant at any chosen value within these limits, and afterthe development of the color is substantiallycomplete oxidizing thereduced dye on the fibers.

3. In the process for dyeing textile fibers with vat colors the stepswhich comprise padding the fibers with a caustic alkali solution of thereduced colors and developing the colors on the fibers by subjectingthem, while the color is in substantially the reduced form to a mildalkaplete, said developing solution having an alkalinity of from aboutpH 8 to about pH' 12 and maintaining the alkalinity of the solutionrelatively constant at any chosen value within these limits saiddeveloping solution containing at the start a sufficient amount of thecolors employed in the padding operation to approximate the amountnecessary to establish equilibrium between the amount of color comingoil of the fibers being dyed and the amount going onto the fibers fromthe developing solution during the developing operation, and after thedevelopment of the color is substantially complete oxidizing the reduceddye on the fibers.

4. In the process for dyeing textile fibers with vat colors the stepswhich comprise padding the fibers with a caustic alkali solution of thereduced colors and developing the colors on" the fibers bysubjectlng'them, while the color is in substantially the'reduced statetoa mild alkaline fibers by subjecting them, while the color is 'insubstantially the reduced state to a mild alkaline solution of an alkalimetal hydrosulfite the alkalinity'of which solution is between pH 10.5and pH 12 while maintaining the alkalinity relatively constant at anychosen value within these limits,

said developing solution containing at the start a sufiicient amount ofthe colors employedin the padding operation to approximate the amountnecessary to establish equilibrium between the amount 01' color comingofi of the fibers being dyed and the amount going onto the fibers fromthe developing solution during the developing operation, and after thedevelopment of thecolor is substantially complete oxidizing the reduceddye on the fibers.

6. In the dyeing of fibers with vat colors by continuous .dyeingprocesses wherein the fiber is padded with a caustic alkali solution ofthe ree duced color, the steps which comprise passing the fibers into adeveloping bath while the dye is in substantially the reduced state,said developing bath being an alkaline hydrosulfite solution having a pHof from 10.5 to 12 and maintainingthe alkalinity of the developingsolution relatively constant at any chosen value within these limitsduring the developing operation, and after the development of the coloris substantially complete oxidizing the reduced dyeon the fibers. i

7. A process of dyeing textiles containing caustic alkalisensitivefibers which comprises padding the textiles with a caustic alkalisolution of a reduced vat colorand immediately passing the padded fabricinto a development solution of sodium'carbonate and an alkali metalhydrosulfite, maintaining the alkalinity of the solution at a sodiumcarbonate content of from 0.5 to 2.5

ounces per gallon of solution, sufllcient alkali hydrosulfite beingpresent in the development solution to retain the color in the reducedstate at all times, and after the development of the color issubstantially complete oxidizing the reduced dye on the fibers.

8. A process of dyeing textilescontaining causat a sodium carbonatecontent of from 0.5 to2.5 ounces per gallon of solution with sufllcientalkali hydrosulfite in the solution to retain the color in the reducedstate at all times, said developing solution containing .at the start asufllcient amount of the colors employed in the padding operation toapproximate the amount necessary to establish equilibrium between theamountot color coming off ofthe fibers being dyed and the amount goingonto the fibers from the developing solution during the developingoperation, and after the development of the color is substantiallycomplete oxidizing the reduced dye-on the taining a sodium carbonatealkalinity in the solu-e tion within relatively narrow limits during therun. and after the development of the color is substantially completeoxidizing theireduced dye on the fibers. V I g V 1 0. In the process fordyeing textile fibers with wit colors the steps which comprise paddingthe fibers with'a caustic alkali solution of the -re-- duced colorsanddev'eloping the colors on the fibers by subjecting them to a mildalkaline solution of an alkali'rnetal hydrosulfite until developmentofthecolor is substantially complete, said developing solution having analkalinity of from about pH 8 to about pH 12, and after the developmentof the color is-substantiaily complete oxidizing the reduced dye on thefibers.

411. In the process for dyeing textile fibers with vatcolo'rs the stepswhich comprise padding'the fibers with a caustic alkali solution of thereduced colors'and developing the colors on the fibersoy subjectingthem'to a mild alkaline solution of an alkali metal hydrosulfite untildevelopment of the color is substantially complete, saiddevelcpingsolution having an alkalinity of from about pH 8 to about pH 12 andmaintaining the alkalinity of the solution relatively constant at anychosen value within these limits and after the development of the coloris substantially complete oxidizing the reduced dye on the fibers.

